1. Field Of The Invention
The invention relates to a process for the production of (.+-.)-2-azabicyclo[2.2.1]hept-5-en-3-one having the formula: ##STR1##
2. Background Art
2-Azabicyclo[2.2.1]hept-5-en-3-one is a bicyclic lactam which is suitable as starting material for the synthesis of carboxylic nucleoside analogues [S. Daluge and R. Vince, J. Org. Chem., Vol. 43, (1978), page 2311]. Such nucleoside analogues are of interest because of their antiviral and chemotherapeutic properties as potential anti-tumor agents. A known synthesis of 2-azabicyclo[2.2.1]hept-5-en-3-one starts from 1,3-cyclopentadiene, which forms with chlorosulfonylisocyanate in a 1,2 addition a bicyclic N-chlorosulfonyl-.beta.-lactam, which is rearranged in the corresponding 1,4 addition product and provides the target compound by hydrolytic cleavage of the N-chlorosulfonyl group in poor yield (27.5 percent) [J. R. Malpass and N. J. Tweddle, J. Chem. Soc. Perkin I, (1977), page 874].
Another known synthesis is based on the Diels-Alder reaction of cyclopentadiene with p-toluenesulfonyl cyanide. In this case, a tosyl-azanorbornadiene results first, which is converted by acid or alkaline hydrolysis into the target compound [J. C. Jagt and A. M. van Larsen, J. Org. Chem., Vol. 39, (1974), page 564,; S. Daluge and R. Vince, loc. cit.]. Drawbacks of this process are the explosiveness of p-toluenesulfonyl cyanide and the unfavorable quantitative ratio of the product to the by-product p-tolylsulfinyl-p-tolylsulfone. Moreover, the cyclopentadiene is used in great excess which has to be distilled off prior to the hydrolysis.